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Old 05-27-2010, 09:35 AM   #21
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Re: Ventilation


I forgot to maention that my future plan (whether it happens or not) is to tear the whole roof off, build eight foot walls and then frame a whole new roof which would take care of all these problems. I got the house for next to free, it's the last piece of property in town on the bluff and on the river so it does not bother me to have to put money into it.
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Old 05-27-2010, 09:41 AM   #22
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Re: Ventilation


Closed Cell foam would be the best option, no venting required (2 lifts approx 4" total - should fill cavities nicely) - if you need more you can fir down, add rigid board to bottom of rafters, etc...

If you feel you need to vent - you can still go CC, then add another layer of sleepers and sheathing above the existing sheathing (or you can go with Concrete Roof Tiles - not sure if that look works in your area)

Closed Cell to expensive? You might look up an article from Fine Home Building (Maybe 4 months ago?) for methods of adding 4" of Rigid foam above the existing sheathing and other systems that I don't have the space to get into here.

EDIT: just saw your new post, based on the "whether it happens or not" part, my answer stands - sure you could cheap out now, but if the "or not" part comes into play, you might be kicking yourself for years to come
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Old 05-27-2010, 10:40 AM   #23
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Re: Ventilation


Attic ventilation is for venting
moisture from the home, as well
as consideration for the shingles.
Moisture should be addressed mechanically
if one uses foam and/or vapor barriers.
One might be surprised at how much
water vapor is introduced to the house
from cooking, bathing, and breathing,
not to mention the differences in relative
humidity for indoor vs outside air.
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Old 05-27-2010, 12:42 PM   #24
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Re: Ventilation


Neo - yes but no - a tight house needs proper ventilation, but that is completely separate from the roof venting

Internal moisture in many cases will not migrate that far, as it would have to get past the paint, drywall, vapor barrier (for all of you up north), etc... and start soaking into any dry surfaces like sheathing, studs, underlayment

Internal moisture control needs to be handled with oven and bath fans. Controlled ventilation is optimal using an HRV or ERV
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Old 05-27-2010, 12:47 PM   #25
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Re: Ventilation


That's my story,
I'm sticking to it! :
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Old 05-27-2010, 05:03 PM   #26
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Re: Ventilation


I'm not going to stick my foot in my mouth so I'm going to say what I believe. Vapor barriers are made to keep moisture out of the living areas as cold weather from outside is introduced to climatized materials on the inside of your home and vis versa. Better your vapor barrier collect moisture than the back side of your drywall and roof vrntilation is mostly needed for both moisture issues and to keep your roofing material from deteriorating faster. My two cents!!!
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Old 05-27-2010, 05:59 PM   #27
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Re: Ventilation


Vapor barriers are only used up north & that is actually to keep the interior moisture from getting into the insulation / framing and condensing (remember Heat moves to Cold & your Dew Points)

The attic - the bulk of the moisture entering there will generally be from the exterior through the soffit or gable vents, venting the roof does nothing to control the moisture, it just moves it around

The good ole shingle life is severely decreased - ok, but only by a week or two due to a slightly higher temperature (1 to 5 degrees per one study) --- now forget all the studies or other BS you might have heard, do you have a better warranty on your shingles because you live in Iowa? I mean Phoenix AZ will have higher shingle temperatures than where you live, correct? I don't ever recall seeing a warranty matrix on a package of shingles based on where you live, have you? The biggest issues with shingles, is the installation & proper care.
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Old 05-27-2010, 06:01 PM   #28
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Re: Ventilation


Quote:
Originally Posted by brendanstl View Post
I forgot to maention that my future plan (whether it happens or not) is to tear the whole roof off, build eight foot walls and then frame a whole new roof which would take care of all these problems. I got the house for next to free, it's the last piece of property in town on the bluff and on the river so it does not bother me to have to put money into it.
Closed cell foam is the only solution I see to insulating this space. Relying on a ridge vent, and holes drilled through the rafters to provide ventilation would be optimistic at best. If your serious about ripping off the roof and building full height walls, I would avoid investing in closed cell foam, and instead run baffles from the ridge vent down as far as you can in every rafter bay. Even this solution wouldn't work that well, but it should give you just enough ventilation until you rip it all off.

If this might end up being permanent, go closed cell .
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Old 05-27-2010, 06:20 PM   #29
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Re: Ventilation


Quote:
Originally Posted by SLSTech View Post
Vapor barriers are only used up north & that is actually to keep the interior moisture from getting into the insulation / framing and condensing (remember Heat moves to Cold & your Dew Points)

The attic - the bulk of the moisture entering there will generally be from the exterior through the soffit or gable vents, venting the roof does nothing to control the moisture, it just moves it around

The good ole shingle life is severely decreased - ok, but only by a week or two due to a slightly higher temperature (1 to 5 degrees per one study) --- now forget all the studies or other BS you might have heard, do you have a better warranty on your shingles because you live in Iowa? I mean Phoenix AZ will have higher shingle temperatures than where you live, correct? I don't ever recall seeing a warranty matrix on a package of shingles based on where you live, have you? The biggest issues with shingles, is the installation & proper care.
Here's my case Sean.
In poorly vented attics, in the winter,
I see frost/ice crystals on the underside
of the deck.
By my lights, that is moisture that
should/could be vented to the out side.
It occurs even when the bath
and range vents are properly exited.
Old plaster with oil paint may not
allow the vapor through the ceiling,
but in those houses there are usually
plenty of leaks to the attic at the access
and ceiling fixtures.
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Old 05-27-2010, 06:48 PM   #30
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Re: Ventilation


Neo - in this case it would be interesting to know where that moisture was coming from and try to get that fixed along with fixing the venting... BUT, this only applies to roofs that are vented.

Now if this roof was a hot roof (using closed cell foam) - you wouldn't have this issue as any humid air could not get to the point where it could condense --- open cell foam on the other hand would allow that moisture to start collecting against the sheathing & will start causing issues
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Old 05-27-2010, 07:57 PM   #31
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Re: Ventilation


Quote:
Originally Posted by SLSTech View Post
Neo - in this case it would be interesting to know where that moisture was coming from and try to get that fixed along with fixing the venting... BUT, this only applies to roofs that are vented.

Now if this roof was a hot roof (using closed cell foam) - you wouldn't have this issue as any humid air could not get to the point where it could condense --- open cell foam on the other hand would allow that moisture to start collecting against the sheathing & will start causing issues
On the other hand if there is a vapor barrier on the living side of the open cell insulation there should be no heat loss and therefore no moisture issues at the air gap between the insulation and the sheeting. Maybe I'm overlooking something
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Old 05-27-2010, 08:05 PM   #32
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Re: Ventilation


http://www.buildingscience.com/docum...r_code_changes
http://www.buildingscience.com/docum...es?full_view=1

And there is more.....
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Old 05-27-2010, 09:02 PM   #33
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Re: Ventilation


Quote:
Neo - in this case it would be interesting to know where that moisture was coming from and try to get that fixed along with fixing the venting... BUT, this only applies to roofs that are vented.
My last house was framed similar to what
I see in those pics.The attic always had tons
of moisture/frost balls on nails.
Near as I could figure,all the heat that
was lost through lower the side walls would
rise up through the balloon framing and into
the attic carrying the moisture with it.

Since this looks like balloon framing,
I would also address getting some insulation,if
there isn't any, into the side walls to stop
that upper migration of moisture.

With the stucco exterior,I would
almost think a vapor barrier would be needed
on the inside of lower side walls to keep moisture
from getting to where it may get trapped.
I've seen older homes start losing paint on the
exteriors after blown-in side wall insulation was installed.
I believe this because of the migration of moisture out through the back of the siding.
Don't know the permeability of stucco,but once
you change the air flow in an existing structure,you
may open up a whole new can of worms.
Just something to consider.

If you insulate the side walls in that attic space the
natural flow of what was heat loss, may now be trapped
in the side walls along with any moisture.
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Old 05-27-2010, 09:55 PM   #34
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Re: Ventilation


Quote:
Originally Posted by brendanstl View Post
On the other hand if there is a vapor barrier on the living side of the open cell insulation there should be no heat loss and therefore no moisture issues at the air gap between the insulation and the sheeting. Maybe I'm overlooking something
Yes but no - the vapor barrier blocks moisture not heat, thus you eliminate moisture migrating where that sprayed on coating is applied. Then we also have a little issue that a certain company doesn't market it this way & by installing it, you are defeating one of their "selling points" about finding a roof leak

Oldfrt - two problems with insulation being installed in exterior walls
#1 is that some of them have plenty of leaks on the exterior and if that is not dealt with, they can't dry out like they would normally do after major rainstorms, etc... (Originally they could handle gallons of water in those cavities & would dry out quickly - now they can't hold as much, nor dry properly)
#2 exactly what wiring is hiding in those walls, there are quite a few types I would not like to see what the results would be
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Old 05-28-2010, 06:58 PM   #35
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Re: Ventilation


Quote:
Originally Posted by SLSTech View Post
Yes but no - the vapor barrier blocks moisture not heat, thus you eliminate moisture migrating where that sprayed on coating is applied. Then we also have a little issue that a certain company doesn't market it this way & by installing it, you are defeating one of their "selling points" about finding a roof leak

Oldfrt - two problems with insulation being installed in exterior walls
#1 is that some of them have plenty of leaks on the exterior and if that is not dealt with, they can't dry out like they would normally do after major rainstorms, etc... (Originally they could handle gallons of water in those cavities & would dry out quickly - now they can't hold as much, nor dry properly)
#2 exactly what wiring is hiding in those walls, there are quite a few types I would not like to see what the results would be
It has knob and tube but it's being changed out as I go, the attic will now have romex tied into the new service put into the house. I agree with oldfrt about insulating the balloon frame wallsbut in alll actuality the balloon frame walls will now have drywall on them once the rake walls under the valley boards are built and the bulkhead walls are torn out. Come fall I'm going to tear the lathe and stucco off from the exterior, tyvek and side with hardie or a similar product once that is done I will be moving to the interior first floor and gutting all the plaster and lathe and rewiring tieing into the new service, insulating, vapor barrier and then drywalling.
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Old 07-05-2010, 04:58 AM   #36
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Re: Ventilation


Ventilation is one of the basic requirements of a good house. As fresh air is a must to ensure the health of those who live in the house good ventilation is a must. In tropical climes it is not difficult to follow ventilation options when building a house.


Every home needs to be adequately heated to protect family members from getting sick or developing hypothermia. But too much heat can feel uncomfortable during the warm season or in tropical climates and promote the growth of mold or other bacterial invasions that require a warm, moist environment to grow and thrive.


A ventilation system is only one specific part of a total effort to provide a healthy and safe workplace. Equally important are good work practices - including proper storage, material containment, use of personal protective equipment and good housekeeping.
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Old 07-05-2010, 05:58 AM   #37
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Re: Ventilation


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Ventilation is one of the basic requirements of a good house. As fresh air is a must to ensure the health of those who live in the house good ventilation is a must. In tropical climes it is not difficult to follow ventilation options when building a house.


Every home needs to be adequately heated to protect family members from getting sick or developing hypothermia. But too much heat can feel uncomfortable during the warm season or in tropical climates and promote the growth of mold or other bacterial invasions that require a warm, moist environment to grow and thrive.


A ventilation system is only one specific part of a total effort to provide a healthy and safe workplace. Equally important are good work practices - including proper storage, material containment, use of personal protective equipment and good housekeeping.
Nice generic blather. And there's this:
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Old 07-09-2010, 06:59 PM   #38
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Re: Ventilation


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. I do not also think that the furring will add any structural support, infact I do think the furring would increase the load the rafters carry... so the decision is yours on what to do. It's a tricky situation you have.
.
The furring will add almost nothing to increase the load capacity of the rafters. The problem is at the interface between the furring and the rafter.

When these try to flex as one, there is great shear acting at the interface. Nails, or screws will do very little here. Even an onsite applied adhesive cannot be assured to handle the shear.

So in effect these are just acting like two separate pieces of wood, one on top of the other.

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Old 07-10-2010, 11:45 PM   #39
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Re: Ventilation


Do yourself a huge favor and follow Building Science's recommendations. You have a can of worms. The biggest issue I see is a quick fix just causes you greater and more severe problems starting immediately. What about total R-Value of your assembly? You need to bring this building up to modern standards and that means minimum R-42 in your climate. That is seven inches of closed cell foam. What about the structural integrity of the rafters in the field once you remove that "bulkhead wall". It must currently be working in concert with floor framing to create a monolithic structure and if you remove it you have spans much to large for the framing members even if you do sister on another 2x4.

Regarding ventilated assembly with conventional insulation. Be very careful about adding ridge venting and vapor barriers to older homes such as this. They are really prone to air infiltration from literally everywhere in the structure. If your ridge vent total area is greater than your soffit or gable vent area the ridge will suck air from inside your building envelope, including your basement, and you will end up with condensation and frost under your roof deck that will melt when exterior temperature reaches a temperatures in the low 30's. If you have vapor barrier up that moisture becomes trapped and runs down your ceiling and walls. Additionally, in the summer, if you are using air conditioning, that same vapor barrier becomes a place for moisture to condense-- remember temperature pushes moisture from warm to cold-- so warm moist outside air is pushed from outside to inside where it condenses on the cool plastic running down and wetting your framing etc and creating mold because it is a warm moist environment.

Second recommendation: forget first phase and do second phase now AND STUDY UP ON THE BUILDING SCIENCE. It will be money better spent and a lot less time wasted on your part.
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Old 07-16-2010, 06:45 AM   #40
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Re: Ventilation


Hi,
I think that the problem might be during the winter, the warm, moist air from your heating system gets trapped in the attic. This causes snow on the roof to melt. When the outside air temperature drops, the melted snow freezes into ice and causes ice dams. Ice dams often lead to roof leaks and shingle damage. You can try there are two types of attic and roof vents: intake and exhaust vents. Intake vents are those placed along the soffit (the area under the overhang). They allow fresh air into the attic. Exhaust vents are installed in the upper third of the roof to allow the air in the attic to escape.

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